This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 8 |
| 6 | 40 |
| 7 | 720 |
| 8 | 1680 |
| 9 | 13440 |
| 10 | 362880 |
| 11 | 1209600 |
| 12 | 4435200 |
| 13 | 68428800 |
| 14 | 296524800 |
| 15 | 29059430400 |
| 16 | 1307674368000 |
| 17 | 6974263296000 |
| 18 | 118562476032000 |
| 19 | 6402373705728000 |
| 20 | 445586448384000 |
| 21 | 1430277488640000 |
| 22 | 51090942171709440000 |
| 23 | 374666909259202560000 |
| 24 | 8617338912961658880000 |